Model Airplane Club, California, USA
Model Airplane Club, California, USA


For Single Cylinder Engines, the Lock Ring Throttle
  For Multiple Cylinder Engines, the GRV 73U

Lock Ring Throttle  Patent Pending

On some single cylinder CO2 engines rotation of the cylinder 110º gives speeds from wide open to tick over.
For the engines listed below we have Otto Kuhni's new lock ring throttle.
Cost is $20.00 per set up.
  1. Remove the cylinder from the crankcase.
  2. Remove the stock lock ring.
  3. Install the new lock ring. This is tapped M1.4, (6) places, at 60º.
  4. For FREE LIGHT, install the new "O" Ring over the cylinder, under the lock ring. This creates the necessary friction to hold the cylinder in adjustment.
  5. On the G-63 engine only, slip the aluminum sleeve over the upper cylindrical part of the crankcase.
  6. Now, screw the cylinder into the crankcase.
  7. Next, rotate the cylinder for the proper R.P.M. Then set the lock ring against the "O" Ring. Now, install the lever arm into one of the six holes. Screw it into the lock ring so the lever arm jams the lock ring onto the cylinder threads. Be careful not to strip the M1.4 thread.
  8. Now, screw the M1.4 x 3 screw into the lock ring, to assist in holding the lock ring securely on place. Also be careful not to strip the thread.
  9. Add the clevis to the lever arm if you wish to adjust the engine RPM with a servo. Please note that for Radio Control the "O" Ring, (see 4, above) is omitted.

Operating Instructions for the
universal regulation valve
for 56 ccm engines and larger.

TWO LEFT AS OF 1-31-14
  GRV 73U Regulation Valve

Setting of or a change in the speed of the two-cylinder CO2 motor in the model is not so easy. In order to facilitate setting of speed of the two-cylinder GMW 73T motor, the motor was fitted with the speed regulation valve GRV 73T. The gas inlet and outlet of the GRV73U universal regulation valve is adapted for connection of other single-cylinder and multi-cylinder CO2 motors as well. This assembly supports also a remote control of the valve and speed by the servo-drive.

The regulation valve GRV73U is connected to the motor gas inlet and regulates its speed by throttling the inlet of gas into the motor cylinders. The valve is adapted for the assembly on the rear side of the motor partition.

The instructions with the valve clearly show the construction of the regulation valve. Cost of this valve is $50.

The needle of the valve adjustment screw falls with its cone into an aperture of the plastic seat of the valve and it can open or throttle the quantity of gas flowing from the tank to the motor. By using the control lever you can turn the screw of the valve with the needle, while adjusting the speed. The control lever is attached to the valve screw by means of a screw M1.2, with which it is possible to set the lever position against the valve screw for the motor speed regulation range required. The eccentric support plate contains a column with a stop screw M1.2 x 8, with which it is possible to set the control lever position for a minimum speed of the motor. Setting of the stop screw is ensured against the stop column with a knurled locking nut on the screw. It is possible to slide the pulling rod onto the control lever of the valve for the purpose of the of servo drive connection. The gas inlet and outlet of the valve contain brass inserts for soldering or gluing of the pipes into the tank and the motor.

Valve connection into the gas inlet of your motor:

The GRV73U universal regulation valve is delivered in assembled condition. Before removing brass inserts from the gas inlet and outlet make sure to compare properly the assemblies of the gas inlet and outlet parts, according to the valve drawing. Remove the inserts and pull off the sealing O-rings from them. The inserts are made of brass and they are pre-drilled with holes of a diameter of 1 mm. The diameter of these holes can be enlarged, depending on the pipes of your motor. Before soldering or gluing the pipes into the inserts do not forget to slide the other parts serving for gas inlet and outlet onto the pipe in appropriate order and orientation according to the drawing.

Setting of the valve for the motor speed regulation range required.

CO2 motor with the regulation valve GRV73U is set to the maximum speed required at the opened valve. By closing the valve you will regulate the speed to the minimum speed required. The control lever position for the minimum speed will be set with the stop screw and ensured with a lock nut on the screw. The movement angle of the control lever at the regulation is generally 60 to 90°.

It is important to note, that the regulation valve regulates speed in the useable range of motor run, to a significant gas pressure drop in the tank at the end of the motor run. The valve functioning depends on gas consumption of your motor. Regulation will be more efficient in the case of motors featuring larger consumption.

The GRV73U universal regulation valve is delivered with the pre-set regulation range. During the first tests of your motor with the valve it is necessary to identify the control lever positions for minimum and maximum speed of the motor. If you lock the needle position with tweezers, you can set the control lever position for the speed regulation range required.

I wish you much success and pleasure with your GRV 73U regulation valve!

24 hour message machine:
(818 ) 718-1685
Roy E. Hanson Jr.
21410 Nashville Street
Chatsworth, CA 91311